[Change and analysis of background concentration of air pollutants in north China during 2008 Olympic Games].

To understand the atmospheric background in North China and evaluate the effect of pollutant emission control as well as the influence of contaminant transportation in the regional pollution, during the 2008 Olympic Games, concentrations of four main air pollutants were observed from June to November at Xinglong station which is the regional background station of North China. We compared the concentrations and diurnal variations in different periods, analyzed the pollution transportation using the ground meteorological data and the backward trajectory model and compared the concentrations between different observation stations in Northern China. The results indicated that the concentrations of NOx, SO2, O3 and PM2.5 in summer were 8.4, 10.5, 126.0 and 59.8 microg x m(-3) respectively and in autumn were 11.7, 17.2, 97.5 and 30.7 microg x m(-3) respectively. During the period of Olympic (2008-08-08-2008-08-24), the concentrations of NOx, SO2, O3 and PM2.5 were 6.6, 6.8, 100.5 and 33.3 microg x m(-3) and reduced 29.0%, 46.9%, 18.6% and 36.5% respectively compared to the average concentrations of the period before and after Olympic Games. The concentration of NOx has reduced 62.5% and the PM2.5 has reduced 29.0% compared to the same term of Olympic in 2007. The air quality has obvious improvement in North China during the Olympic Games. Before the emission control, the concentrations of pollutants were lower in the night and became higher gradually in the daytime and reached the peak values in 17:00-20:00 which can indicate the accumulation of regional pollution transportation in Xinlong. In the emission control period, the accumulation of pollutants in afternoon was obviously weakened and the transportation of pollutants was lower which can reveal the obvious effect of the emission control in Beijing and peripheral areas. The atmosphere in Xinglong was mainly influenced by the monsoon from south direction in summer and autumn and the pollution of Xinglong was seriously influenced by the regional pollution in the south direction. Compared the concentrations between different stations, we can conclude that in summer and autumn the pollutions of NOx and SO2 are relatively lower, the pollution of O3 is not allowed to be optimism and the pollution of PM2.5 is very serious which should be paid enough attentions to.